The present invention relates to a water-swellable caulking material for preventing water leakage through a construction or expansion joint of concrete or, more particularly, to a water-swellable caulking material for water-leakage prevention protected on the surface with a temporary water-impervious film so that inadvertent contacting of the caulking material with underground water, rain water and the like neutral water before the application thereof to a construction joint never causes premature or untimely swelling and expansion of the material which can commence only in contact with an alkaline water contained in a concrete mixture as a result of the decreased imperviousness of the temporary water-impervious film by the alkali. The invention also relates to a method of preventing leakage of water through a construction joint by use of the same.
Needless to say, water-leakage preventing caulking materials are very important and widely used in civil engineering and building construction works to prevent leakage of water by filling an interstice responsible to water leakage such as cracks, fissures and intersticial gaps in concrete works, water pipes and joints thereof and the like.
Traditional water-leakage preventing caulking materials are shaped of a water-resistant, readily deformable material as the base such as rubbers, flexible plastics, bituminous materials and the like. These base materials are not free from a problem accompanying the decrease of the resilient elasticity or appearance of the phenomenon of creeping unavoidable in a prolonged service over a long period of time resulting in the loss of accomodation to the changes in the dimensions of interstices to cause water leakage.
As a remedy for the above mentioned problem, water-swellable caulking bodies have been developed and proposed in Japanese Patent Kokai No. 57-108143 and 57-135160 teaching a water-swellable vulcanizate of a composition comprising a highly water-absorptive resin, dienic rubber, vulcanizing agent, vulcanization accelerator, filler, aging retarder and the like or a composite body composed of such a water-swellable vulcanizate and a non-swellable polymeric material such as a vulcanizate of a composition comprising a dienic rubber, vulcanizing agent, vulcanization accelerator, filler, aging retarder and the like. Further, a water-swellable resinous composition is also proposed in Japanese Patent Kokai No. 56-3424 which comprises a thermoplastic synthetic resin having flexibility such as a copolymer of ethylene and vinyl acetate impregnated with a highly water-absorptive resin.
The caulking materials of the above described water-swellable type can provide an efficient means for water-leakage prevention due to the completeness of caulking to fill up the interstices responsible to the leakage of water by virtue of the high swelling pressure produced when the caulking material is contacted with water so that they are very useful along with easiness of application thereof to any interstices. A problem in the water-swellable caulking material is, however, that they are liable to a disadvantage of premature or untimely swelling and expansion with water when they are inadvertently contacted with water such as atmospheric moisture, rain water and condensed dew during storage and transportation or with a small volume of water brought into contact with them by chance in the course of working. When the water-swellable caulking material has been prematurely swollen with water, difficulties are sometimes unavoidable in the application thereof or the caulking material may eventually fall down subsequent to application in addition to the fatal drawback of insufficient caulking pressure leading to leakage of water. Moreover, the swollen water-absorptive resin forming the dispersant phase of the composite caulking body may sometimes fall off the surface of the caulking body so that the water-leakage preventing effect is subject to gradual decrease in the lapse of time.
The above described disadvantages can be overcome to some extent by using a pressure-collapsible protecting web, which may be in the form of a woven or non-woven fabric, formed from an emulsion of a synthetic rubber or resin and having a low mechanical strength in the transverse direction as a covering layer for temporarily preventing permeation of water (see, for example, Japanese Patent Publications Nos. 56-29911 and 58-16054). This method of using a temoporary protecting web, however, involves several problems and disadvantages that the production cost of such a caulking material is necessarily high due to the complicated manufacturing process and the caulking material has low versatility in the shapes as a consequence of the use of a woven or non-woven fabric.
The inventors accordingly have undertaken extensive investigations with an object to provide an inexpensive water-leakage preventing caulking material manufacturable in a simple process without the problems and disadvantages in the prior art caulking materials and previously proposed a caulking body formed of a water-swellable polymeric base material and covered with a coating film of low water permeability formed of a synthetic rubber, such as chloroprene rubbers, nitrile rubbers, styrene-butadiene copolymeric rubbers, chlorosulfonated polyethylenes and the like, or a synthetic resin, such as polyvinylidene chlorides, copolymers of ethylene and vinyl acetate and the like. Although the water-swellable caulking material provided with such a coating film can be manufactured in a simple process and at a low cost, it is not always quite satisfactory in respect of the temporary water-imperviousness or water-imperviousness before use like other caulking materials of the type provided with a coating film for controlling the water permeation in time. For example, premature or untimely swelling and expansion of such a caulking material is sometimes unavoidable when the material is inadvertently contacted with water during storage and transportation as well as in the course of working for construction joint of concrete so that the caulking effect is greatly reduced.